Excitation system for vapor electric converters



March 22,1938. D. D. KNOWLES 9 9 EXCITATION SYSTEM FOR VAPOR ELECTRIC CONVERTERS Filed March 5, 1936 v 7 V V wwmsssas; iNVENTOR flewsyfl Know/e5.

$ 43M BYWMW ATTORNEY Patented Mar. 22, 1 938 2,1 1

oni'rso sra'rss rarest oFFicE EXCITATION SYSTEM FOR VAPOR ELECTRIC CONVERTERS Dewey D. Knowles, Wilkinsburg, Pa, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a corporation of Pennsylvania Application March 5, 1936, Serial No. 6?,292

10 Claims. (01. 175363) My invention relates to an excitation system interrupting current flow from either terminal at for a vapor-electric converter, and particularly the end of the desired conducting interval. Howto a make-alive system for an. inverted rectifier. ever, as is well known, the commutating capaci- This application is a continuation as to com tor 8 can be dispensed with when the output fremon subject matter of application Serial No. quency of the converter is established by some 5 690,702, filed September 23, 1933. other means, such as synchronous devices sup In the operation of vapor-electric converters oi plied by the converter or when the frequency is the type employing make-alive electrodes, that established by an independent source in parallel is, electrodes which initiate a cathode spot at with the converter.

10 the beginning of each conducting period, oonsid-- Each of the arc chambers is provided with an 10 erable disadvantage has been found in that the electrode iii composed of suitable resistance mamake-alive electrodes carry considerable excited terial such as carborundum, boron, boron carcurrent, This current is not only detrimental to bide, etc., in contact with the vaporizing cathode the make-alive material but is disadvantageous material 5 i. These make-alive electrodes iii are in that it increases the losses of the converter. Co ted hr gh Suita discharge means 15 t is an object of my invention to provide a such as glow tubes or even simple arc chambers, make-alive circuit in which the current will be to the oppos te S d o a m keve Capacitor furnished to the make-alive electrodes only dur- T pp s t Sides 0 the make-alive p ing the brief interval necessary to create a cathtor i l are connected to the anode terminals EB-l 2D ode spot. of the transformer 5 by means of suitable timing It is a further object of my invention to proresistors iii6. The frequency of the altervide an excitation system which Will automatimating-current O put y b dete ed y cally govern the frequency output of the convarying the es ce in t Charging verter. circuit of the make-alive capacitor i i. For pur- I achieve this advantage by providing a caposes of simplicity of illustration, the timing repacitor in series with a plurality of make-alive SiStOrS 65-45 and the COmmU-tatmg C p t 3 electrodes and governing the discharge of the have been S own as av ng a common conneccapacitor by means of suitable discharge devices, t n to the 91106-8 terminals bu v o y such as glow-tubes or even controlled arc gaps. t e Co a Capacitor 8 0011101 e a S p The timing feature of my invention comprises a rate connection or in certain applications be timing resistor to control the time necessary to Omittfid fl 30 supply sufficient potential to the make-alive ca- The resistors 25-46 are of such value that pacitor to break down the glow-tubes and, cone the direct Current pp ed oss the sequently, form the cathode spot. terminals of the converter, the current flow is not It is a further object of my invention to p1@ sunicient to operate the n1ake-alive electrodes is. 5 vide a method of initiati g'th discha ge in a In order to initiate operation of the converter vapor-electric device acting as an inverted recti when the alternating-Current System 2 is lowerfier when the rectifier i supplying a 1 1, th i gised, I provide a suitable device, such as a switch quency of which is not established by outside I9, and a current limiting resistor Ell, formonienmeans. tarily short circuiting one of the series discharge to Other objects and advantages of my invention devices will be apparent from the following specification, T Start p fi Of y v power is ptaken in conjunction with the accompanying plied to the direct-current line i in such manner drawing, in which: that the positive potential is applied through the 45 Figure l is a schematic illustration of a contransformer 5 to the anodes of the arc chambers 45 verter embodying my invention; and 1, While negative potential is applied to the cath- Fig. 2 is a similar illustration of a modification 05195 i according to my invention. If the alternating-current line 2 is energized, The apparatus according to my invention comthe capacitor i l will be charged and operation prises a suitable direct-current system i and an will follow at once. 0 alternating-current system 2 connected by means Assuming that the alternating-current line 2 of a converter having a plurality of discharge oeenergized, the positive potential will be apchambers 5 fed by a suitable transformer plied to both terminals 5 and l with the result Preferably, the terminals E'i of the tran former that the capacitor M will not receive a charge 5 are provided with a suitable capacitor 8 for and the line voltage is thus applied across tubes 55 I2 in series with the make-alive electrode l and the timing resistance l5l6. The resistance of the resistors |5l6 is sufliciently high that the current through tube I2 is of such a low value that the current in the make-alive electrodes I0 is not sufficient to create a cathode spot and the device remains inactive. Now, by closing the key l9 connecting the one side of the capacitor M to the negative side of line I, the condenser I4 is allowed to charge to substantially line voltage. The charged capacitor I4 will then discharge through the right-hand tube l2 and initiate a cathode spot in tube 4, at which time key If! should be opened to permit charging of capacitor 14 in the opposite direction.

The device then will operate at a frequency dependent upon the resistance of resistors l5i6. Obviously, the frequency may be varied by changing the value of resistance of resistors |5l5.

In the modification according to Fig. 2, suitable unidirectional conductors 26 are inserted between the negative side of line I and the opposite sides of the capacitor M, in order to pro-- vide a low impedance return path for the makealive current. This materially reduces the energy consumption of the make-alive system and also reduces the danger of arc-back in the inactive valve 4. While key I9, arranged as shown in Fig. 1, may be utilized to initiate operation, I prefer to provide a key around one of the timing resistors, such as Hi, to apply the line potential directly to one of the control tubes !2. Suitable means, such as a capacitor 3|, should be provided for limiting the duration of current flow through the starting circuit. The key 30 should be opened as soon as the make-alive current has been terminated by the capacitor 3!, in order to prevent interference with the timing of the makealive system by the resistors |5--|5.

By changing the resistance l5 of the timing circuit supplying potential to the make-alive capacitor M, the frequency of the alternating-current may be satisfactorily governed.

While I have shown and described for purposes of illustration specific embodiments of my invention, it will be apparent to those skilled in the art that changes and modifications can be made therein without departing from the true spirit of my invention or the scope of the appended claims.

I claim as my invention:

1. A Vapor-electric converter particularly for converting direct current to alternating current comprising a plurality of arc-chambers, a pair of main electrodes in each arc chamber, a transformer for feeding current to the converter, a commutating capacitor associated with said transformer, a make-alive electrode in each arc chamber, an excitation condenser for supplying current to said make-alive electrodes, an are discharge device in series with each of said makealive electrodes and resistance means for charging the excitation condenser from the transformers.

2. A vapor-electric converter particularly for converting direct current to alternating current comprising a plurality of arc-chambers, a pair of main electrodes in each arc chamber, a transformer for feeding current to the converter, a commutating capacitor associated with said transformer, a make-alive electrode in each arc chamber, an excitation condenser for supplying current to said make-alive electrodes, an are discharge device in series with each of said makealive electrodes and resistance means for charging the excitation condenser from the transformer, and a circuit for initially charging the condenser.

3. An ignition system for a vapor-electric converter comprising a plurality of arc chambers, means for controlling current flow to said arc chambers, an ignition electrode in each of said chambers, a condenser for each pair of arc chambers, the ignition electrodes in said pair of arc chambers being connected to opposite sides of said condenser, an auxiliary discharge device in series between each of said electrodes and said condenser and means for alternately charging the condenser in reverse direction.

4. An ignition system for a vapor-electric converter comprising a plurality of arc chambers, means for commutating current between said are chambers, an ignition electrode in each of said chambers, a condenser for each pair of arc chambers, the ignition electrodes in said pair of arc chambers being connected to opposite sides of said condenser, an auxiliary discharge device in series between each of said electrodes and said condenser, an inductive winding for supplying current to said converter and timing resistances connected between opposite sides of said condenser and the respective ends of said Winding.

5. A conversion system comprising a vaporelectric converter having a plurality of discharge chambers, an anode and a cathode in each chamber, means for commutating current between said chambers, an auxiliary electrode in each chamber, said auxiliary electrode being adapted for initiating a cathode spot on said cathode, a supply system for the auxiliary electrodes comprising a capacitor, said auxiliary electrodes being connected to opposite sides of said capacitor, timing resistances connected to the opposite sides of said capacitor and the anodes of the respective discharge chambers, and are discharge devices connected between the capacitor and the auxiliary electrodes for applying the potential of the capacitor to the auxiliary electrodes.

6. A vapor-electric conversion system comprising an alternating and a direct-current line, a vapor-electric converter having a plurality of discharge chambers, a pair of main electrodes in each of said chambers, an inductive winding for supplying current to said main electrodes, means for controlling current flow from said winding to said discharge chambers, an auxiliary electrode associated with one of the main electrodes in each chamber for initiating a cathode spot therein, a

capacitor for supplying current to said auxiliary electrodes, connections from the inductive winding to said capacitor for supplying potential thereto, timing means in said connections, said capacitor being connected to each of said auxiliary electrodes and discharge means between said capacitor and said electrode for controlling the passage of current to said electrodes.

'7. A vapor-electric conversion system comprising an alternating and a direct-current line, a vapor-electric converter having a plurality of discharge chambers, a pair of main electrodes in each of said chambers, an inductive winding for supplying current to said main electrodes, con denser means for controlling current flow from said winding to said discharge chambers, an auxiliary electrode associated with one of the main electrodes in each chamber for initiating a cathode spot therein, a capacitor for supplying current to said auxiliary electrodes, connections from the inductive winding to said capacitor for supplying potential thereto, said capacitor being connected to each of said auxiliary electrodes and discharge means between said capacitor and said electrode for controlling the passage of current to said electrodes and resistances in the connections between the winding and the capacitor for timing the charge thereon.

8. An ignition system for a vapor-electric converter having a plurality of arc chambers and means for distributing current to said chambers comprising an auxiliary electrode in each of the arc chambers, a capacitor for supplying current to said electrodes, a connection for supplying charging current to said capacitor, voltage responsive discharge means for applying the capacitor potential to said electrodes, and a connection for securing an initial charge on said capacitor.

9. An ignition system for a vapor-electric converter having a plurality of arc chambers and means for distributing current to said chambers comprising an auxiliary electrode in each of the arc chambers, a capacitor for supplying current to said electrodes, a connection for supplying charging current to said capacitor, voltage responsive discharge means for applying the capacitor potential to said electrodes, and a connection for providing initial current flow to one of said auxiliary electrodes.

10. A conversion system comprising a vaporelectric converter having a plurality of discharge chambers, an anode and a cathode in each chamber, means for controlling current flow to said chambers, an auxiliary electrode in each chamber, said auxiliary electrode being adapted for initiating a cathode spot on said cathode, a supply system for the auxiliary electrode comprising a capacitor, said auxiliary electrodes being connected to opposite sides of said capacitor, timing resistances connected to said capacitor and to the anodes of the discharge chambers for supplying potential thereto, arc discharge devices for applying the potential of the capacitor to the auxiliary electrodes, and a low impedance return circuit for said capacitor.

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